Your copy of the contract should tell you.
Don't panic yet!! Please don't. This can and will probably have a happy ending.
Banks are notorious for being slow in sending funds. In my experience you need to have the solicitor make the request 5 working days before completion.
Your solicitor probably requested too late. As he has requested now, funds are on way.
The heavy penalties for non-completion (non-performance) of the contract, only kick in after you have failed to complete after 3 notices have been served by the vendor.
You didn't complete Friday so a notice will be served Tuesday.
Clearly you're hoping to complete ASAP and your solicitor can convey this to other parties with timescales.
Now the penalties are interest charges for the remainder of the purchase price (ie property price minus deposit = outstanding amount at x% per day of late completion).
That part won't be too bad.
You may also be responsible for lost removal firm costs of other parties in the chain. This will be more expensive.
Generally if removal vans are packed they will go to a depot and there will be a standing charge per night. Obv this is a bank hols weekend so an extra night.
You need to get into your bank first thing and get written confirmation from them that your solicitor requested the funds too late.
Otherwise you will foot the bill for solicitor and bank blaming each other.
If funds were requested in time, you may have some comeback against the bank but they usually exclude this as part of their agreement.
Until you get hold of the bank, you can be 100% that its the solicitors fault.
Unless of course he already has owned up to screwing up.
Either way you're correct to be hopping mad.
Fwiw I've been involved in commercial property for more than 15 years and all I can say is never ever schedule completion for a Friday!